The field of the invention is synthetic resins having pore forming. The present invention is particularly concerned with the production of expandable styrene polymers which, due to a small quantity of an incompatible high molecular weight compound, homogeneously dispersed throughout the styrene polymers and forming a non-continuous phase can be fabricated into quickly moldable cellular bodies.
The state of the art of foamed polystyrene, and the poly-1-butene used in the present invention may be ascertained by reference to the Kirk-Othmer "Encyclopedia of Chemical Technology", 2nd Ed., Vols. 3 (1964) under the section entitled "Butylenes", pages 830-865; 9 (1966), under the section entitled "Foamed Plastics", pages 847-884; 19 (1969), under the section entitled "Styrene Plastics", pages 85-134; and the Supplement (1971), under the section "Polymers of 1-Butene", pages 776-789, the disclosures of which are incorporated herein.
Vol. 3 of Kirk-Othmer discloses, at page 832, the nomenclature and physical properties of 1-butene, and in Table 5 on pages 850-853, the reactions of 1-butene. The Supplement volume of Kirk-Othmer discloses, in Table 11, beginning at page 786, the copolymerization of 1-butene with 1-olefins. Volume 9 discloses foamed polystyrene, particularly at pages 852 and 855, and volume 19 discloses the polystyrene foams, particularly at pages 116 through 120.
The disclosure of U.S. Pat. No. 3,503,905 of Ludwig Zuern et al which issued Mar. 31, 1970 is also incorporated herein. This patent discloses the state of the art of expanding styrene polymers in molds, styrene molding compositions which can be removed from the molds after relatively short minimum residence times, styrene polymers and copolymers containing at least 50 percent by weight of styrene units useful in the present invention, foaming agents useful in the present invention and the methods of homogeneously dispersing the poly-1-butene in the molding materials.
It is known in the prior art to produce foamable molded bodies by expanding inflatable particulate styrene polymers in molds. According to this process, particulate inflatable styrene polymers are, with the help of steam or hot gases, subjected to a pre-expansion process. The prefoamed particles are then stored and further expanded in a perforated pressure-resistant mold by means of superheated steam so that they fuse together to form a molding whose dimensions correspond to those of the mold's internal cavity. This step is known as molding. After molding, the article thus obtained is cooled in the mold. Cooling must be continued until the internal sections of the article have cooled to a temperature below the softening point of the styrene polymers. If it is removed from the mold beforehand, deformation may result. Since foam plastics are good insulators, relatively long periods are necessary to cool the moldings. The period after which the article may be removed from the mold without there being any subsequent deformation is usually called the minimum residence time. This minimum residence time, which also includes the cooling time, creates idle time which one tries to keep it as short as possible for the optimum employment of the molds.
A series of methods are known whereby the cooling periods are successfully shortened and more quickly moldable molded bodies are arrived at, for example by coating the expandable or prefoamed particles with paraffin as disclosed in British Patent No. 1,083,040 and West German Published Application No. 1,959,729, or with oil-soluble emulsifiers as disclosed in British Patent No. 1,174,749. Furthermore, quickly moldable cellular bodies may be arrived at when the expandable particles are produced in finely divided form containing a small amount of water, as disclosed in West German Published Application No. 1,719,318, or when the manufacture of the expandable particles by polymerization is undertaken in the presence of a small amount of a definite bromine compound, as disclosed in U.S. Pat. No. 3,503,905 and West German Published Application No. 1,297,327. A series of known processes carry out the polymerization in the presence of a small amount of polymer that is incompatible with the polystyrene as disclosed in West German Published Application Nos. 1,520,790; 1,769,374; 2,101,666; 1,570,238 and U.S. Pat. Nos. 2,857,339; 2,857,340; and Published Japanese Patent Application No. 71/21453, whereby, on the one hand, a shorter cooling time is observed and, on the other, however, the admixtures have practically no influence on the cooling time. Incompatible polymers disclosed in these patents are polyethylene, atactic polypropylene, polyisobutylene, polyvinylchloride, mixed polymers made up of ethylene and vinyl acetate or styrene, acrylic nitrile and N-vinyl carbazole or condensation products from phthalic acid and hexanetriol, besides elastomers such as butadiene-styrene-copolymers, polybutadiene, and polyisoprene. The compounds of high molecular weight according to the state of the art are, however, not satisfactory because they either yield insignificant inflatable particles or allow no satisfactory bonding, or do not lead to shortened cooling periods.